Wavelength division multiplexing system using optical switch

Abstract

An optical switch and a wavelength division multiplexing system utilizing the switch. The multiplexing system comprises an optical bus, an optical source, and a plurality of optical switches. The source provides light on the bus having a plurality of wavelength bands, and the switches are serially connected along the bus. Each switch includes means for reacting to an external stimulus by assuming one of at least two states. In a first state, light in all wavelength bands is transmitted through the switch. In a second state, light in a modulation wavelength band is attenuated, and light in the remaining bands is transmitted, the modulation band being different for each switch. The switch may comprise an optical bandpass filter onto which light from the bus is directed, such that light within the passband is transmitted, and light outside the passband is reflected. The transmitted beam is selectively attenuated in accordance with the external stimulus.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. An optical wavelength division multiplexing system, comprising: an optical bus;   an optical source for providing light having a plurality of wavelength bands and for coupling said light into the bus; and,   a plurality of optical switches serially coupled along the bus, each switch including means for reacting to an external stimulus by assuming one of at least two states, a first state being one in which light in all of said wavelength bands is substantially transmitted through the switch, a second state being one in which light in a modulation wavelength band is attenuated and light in the remaining wavelength bands is substantially transmitted through the switch, the modulation wavelength band being different for each switch, each switch comprising an optical stopband filter having a predetermined stopband and opposed first and second surfaces, means for coupling light from the optical bus onto the first surface of the stopband filter such that light within the stopband is substantially reflected by the stopband filter to produce a reflected beam, and light outside the stopband is substantially transmitted through the stopband filter to produce a transmitted beam, optical path means for causing the reflected beam to follow an optical path and to then strike the second surface of the stopband filter such that the reflected beam is rereflected by the stopband filter and combined with the transmitted beam to produce a recombined beam, the optical path means comprising first and second mirrors, and modulation means for selectively attenuating light traveling along said optical path in accordance with the external stimulus, to thereby selectively pass or attenuate light in said stopband.   
     
     
       2. The multiplexing system of claim 1, wherein for each switch, the modulation means comprises a modulation element that can be moved into an out of a portion of the optical path between the mirrors, to thereby selectively block or transmit light traveling along the optical path. 
     
     
       3. The multiplexing system of claim 1, wherein for each switch, the modulation means comprises a modulation element positioned in the optical path between the mirrors, the modulation element being responsive to an external non-mechanical stimulus to either block or transmit light traveling along the optical path. 
     
     
       4. The multiplexing system of claim 1, wherein for each switch, the modulation means comprises means for diverting light traveling along said optical path between the mirrors such that it is not coupled back onto the bus. 
     
     
       5. A switch for use on an optical bus in an optical wavelength division multiplexing system, the switch comprising: an optical stopband filter having a predetermined stopband and opposed first and second surfaces;   means for coupling light from the optical bus onto the first surface of the stopband filter such that light within the stopband is substantially reflected by the stopband filter to produce a reflected beam, and light outside the stopband is substantially transmitted by the stopband filter to produce a transmitted beam;   optical path means for causing the reflected beam to follow an optical path and to then strike the second surface of the stopband filter such that the reflected beam is rereflected by the stopband filter and combined with the transmitted beam to produce a recombined beam;   means for coupling the recombined beam back onto the bus; and   the optical path means comprising first and second mirrors, and modulation means for selectively attenuating light traveling along said optical path in accordance with an external stimulus, to thereby selectively pass or attenuate electromagnetic radiation is said stopband.   
     
     
       6. The switch of claim 5, wherein the means for selectively attenuating light traveling along said optical path comprises a modulation element that can be moved into and out of a portion of the optical path between the mirrors, to thereby selectively block or transmit light traveling along the optical path. 
     
     
       7. The switch of claim 5, wherein for each switch, the means for selectively attenuating light traveling along said optical path comprises a modulation element positioned in the optical path between the mirrors, the modulation element being responsive to an external non-mechanical stimulus to either block or transmit light traveling along the optical path. 
     
     
       8. The switch of claim 5, wherein for each switch, means for selectively attenuating light traveling said optical path comprises means for diverting light traveling along said optical path between the mirrors such that it is not coupled back onto the bus. 
     
     
       9. The invention of claim 1 or 5, wherein the optical path followed by the reflected beam lies in a plain perpendicular to a direction of travel of the light coupled onto the first surface of the stopband filter, and wherein the optical path means comprises four mirrors.